Environment and dispersal paths override life strategies and residence time in determining regional patterns of invasion by alien plants.

We describe a novel dissimilarity framework to analyze spatial patterns of species diversity and illustrate it with alien plant invasions in Northern Portugal. We used this framework to test the hypothesis that patterns of alien invasive plant species richness and composition are differently affected by differences in climate, land use and landscape connectivity (i.e. Geographic distance as a proxy and vectorial objects that facilitate dispersal such as roads and rivers) between pairs of localities at the regional scale. We further evaluated possible effects of plant life strategies (Grime's C-S-R) and residence time. Each locality consisted of a 1 km(2) landscape mosaic in which all alien invasive species were recorded by visiting all habitat types. Multi-model inference revealed that dissimilarity in species richness is more influenced by environmental distance (particularly climate), whereas geographic distance (proxies for dispersal limitations) is more important to explain dissimilarity in species composition, with a prevailing role for ecotones and roads. However, only minor differences were found in the responses of the three C-S-R strategies. Some effect of residence time was found, but only for dissimilarity in species richness. Our results also indicated that environmental conditions (e.g. climate conditions) limit the number of alien species invading a given site, but that the presence of dispersal corridors determines the paths of invasion and therefore the pool of species reaching each site. As geographic distances (e.g. ecotones and roads) tend to explain invasion at our regional scale highlights the need to consider the management of alien invasions in the context of integrated landscape planning. Alien species management should include (but not be limited to) the mitigation of dispersal pathways along linear infrastructures. Our results therefore highlight potentially useful applications of the novel multimodel framework to the anticipation and management of plant invasions. (C) 2013 Elsevier GmbH. All rights reserved.

Extinction debt of high-mountain plants under 21st-century climate change

Quantitative estimates of the range loss of mountain plants under climate change have so far mostly relied on static geographical projections of species' habitat shifts(1-3). Here, we use a hybrid model(4) that combines such projections with simulations of demography and seed dispersal to forecast the climate-driven spatio-temporal dynamics of 150 high-mountain plant species across the European Alps. This model predicts average range size reductions of 44-50% by the end of the twenty-first century, which is similar to projections from the most 'optimistic' static model (49%). However, the hybrid model also indicates that population dynamics will lag behind climatic trends and that an average of 40% of the range still occupied at the end of the twenty-first century will have become climatically unsuitable for the respective species, creating an extinction debt(5,6). Alarmingly, species endemic to the Alps seem to face the highest range losses. These results caution against optimistic conclusions from moderate range size reductions observed during the twenty-first century as they are likely to belie more severe longer-term effects of climate warming on mountain plants.

Detritivorous crustaceans become herbivores on jasmonate-deficient plants.

The jasmonate signal pathway is known to control defenses against herbivores, such as leaf eaters (folivores). Does the reach of the pathway extend to defense against other types of animal? Among the arthropods attracted to seed baits placed below flowering Arabidopsis thaliana plants are 2 largely nocturnal isopod crustaceans generally considered as detritivores: Porcellio scaber and Armadillidium vulgare. Parallel laboratory experiments identified the isopods as being capable of predation on intact plants. Isopod feeding was strongly facilitated in jasmonate-deficient Arabidopsis and rice plants. The feeding activity of isopods revealed potentially detritivore-sensitive, jasmonate-protected Achilles' heels in these architecturally different plants (petioles and inflorescence stems in Arabidopsis, and lower stem and mesocotyl in rice). The work addresses the question of what stops 2 detritivores from attacking living plants and provides evidence that it is, in part, the jasmonate signal pathway. Furthermore, senescent leaves from an Arabidopsis jasmonate mutant were consumed more rapidly than senescent wild-type leaves, suggesting that past activity of the jasmonate signal pathway in leaves may slow carbon recycling through detritivory.

Plants respond to pathogen infection by enhancing the antifungal gene expression of root-associated bacteria.

Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens.

Plants and tortoises: mutations in the Arabidopsis jasmonate pathway increase feeding in a vertebrate herbivore.

Photosynthetic tissues, the major food source of many invertebrates and vertebrates, are well defended. Many defence traits in leaves are controlled via the jasmonate signalling pathway in which jasmonate acts as a hormone by binding to a receptor to activate responses that lead to increased resistance to invertebrate folivores. We predicted that mutations in jasmonate synthesis might also increase the vulnerability of leaves to vertebrate folivores and tested this hypothesis using the Eastern Hermann's tortoise (Eurotestudo boettgeri) and an Arabidopsis thaliana (Brassicaceae) allene oxide synthase (aos) mutant unable to synthesize jasmonate. Tortoises preferred the aos mutant over the wild type (WT). Based on these results, we then investigated the effect of mutating jasmonate perception using a segregating population of the recessive A. thaliana jasmonate receptor mutant coronatine insensitive1-1 (coi1-1). Genotyping of these plants after tortoise feeding revealed that the homozygous coi1-1 receptor mutant was consumed more readily than the heterozygous mutant or the WT. Therefore, the plant's ability to synthesize or perceive jasmonate reduces feeding by a vertebrate herbivore. We also tested whether or not tortoise feeding behaviour was influenced by glucosinolates, the principal defence chemicals in Arabidopsis leaves with known roles in defence against many generalist insects. However, in contrast to what has been observed with such insects, leaves in which the levels of these compounds were reduced genetically were consumed at a similar rate to those of the WT.

Analysis of the alternative pathways for the beta-oxidation of unsaturated fatty acids using transgenic plants synthesizing polyhydroxyalkanoates in peroxisomes.

Degradation of fatty acids having cis-double bonds on even-numbered carbons requires the presence of auxiliary enzymes in addition to the enzymes of the core beta-oxidation cycle. Two alternative pathways have been described to degrade these fatty acids. One pathway involves the participation of the enzymes 2, 4-dienoyl-coenzyme A (CoA) reductase and Delta(3)-Delta(2)-enoyl-CoA isomerase, whereas the second involves the epimerization of R-3-hydroxyacyl-CoA via a 3-hydroxyacyl-CoA epimerase or the action of two stereo-specific enoyl-CoA hydratases. Although degradation of these fatty acids in bacteria and mammalian peroxisomes was shown to involve mainly the reductase-isomerase pathway, previous analysis of the relative activity of the enoyl-CoA hydratase II (also called R-3-hydroxyacyl-CoA hydro-lyase) and 2,4-dienoyl-CoA reductase in plants indicated that degradation occurred mainly through the epimerase pathway. We have examined the implication of both pathways in transgenic Arabidopsis expressing the polyhydroxyalkanoate synthase from Pseudomonas aeruginosa in peroxisomes and producing polyhydroxyalkanoate from the 3-hydroxyacyl-CoA intermediates of the beta-oxidation cycle. Analysis of the polyhydroxyalkanoate synthesized in plants grown in media containing cis-10-heptadecenoic or cis-10-pentadecenoic acids revealed a significant contribution of both the reductase-isomerase and epimerase pathways to the degradation of these fatty acids.

The ecological significance of arbuscular mycorrhizal fungal effects on clonal reproduction in plants

The population ecology of clonal plants depends on the number and distribution of ramets formed during growth. Variation in clonal reproduction has previously been explained by variation in effects of abiotic resource heterogeneity and by plant genotypic variation. Different co-occurring species of the mutualistic arbuscular mycorrhizal fungi (AMF) have been shown to differentially alter growth traits of Prunella vulgaris which we hypothesize would lead to changes in clonal reproduction. Two experiments were carried out to test whether different co-occurring mycorrhizal fungi significantly influence clonal reproduction of P. vulgaris whether this effect also occurs when P. vulgaris is growing in an artificial plant community and how the effects compare with plant genotype effects on clonal growth of P. vulgaris. In the first experiment the number of ramets of P. vulgaris growing in a plant community of simulated calcareous grassland was significantly affected by inoculation with different mycorrhizal fungi. The number of ramets produced by P. vulgaris differed by a factor of up to 1.8 with different mycorrhizal fungi. The fungal effects on the number of new ramets were independent of their effects on the biomass of P. vulgaris. In a second experiment 17 different genotypes of P. vulgaris were inoculated with different mycorrhizal fungi. There were significant main effects of genotypes and mycorrhizal fungi on clonal reproduction of P. vulgaris. The effect of different mycorrhizal fungi contributed more than the effect of plant genotype to variation in size and ramet production. However mean stolon length and spacer length which determine the spatial arrangement of ramets were only significantly affected by plant genotype. There were no mycorrhizal fungal X plant genotype interactions on clonal growth of P. vulgaris indicating that there is no obvious evidence that selection pressures would favor further coevolution between P. vulgaris and mycorrhizal fungal species. In natural communities plants can be colonized by several different AMF at the same time. The effect of the mixed AMF treatment on the growth and clonal reproduction of P. vulgaris could not be predicted from the responses of the plants to the single AMF To what extent however the patterns of colonization by different AMF differ among plants in a natural community is unknown. Since the effects of AMF on growth and clonal reproduction occur on a population of P. vulgaris in a microcosm plant community and because the effects are also as great as those caused by plant genotypic variation we conclude that the effects are strong enough to potentially affect population size and variation of clonal plants in communities.

Predicting future distributions of mountain plants under climate change: does dispersal capacity matter?

Many studies have investigated the impacts that climate change could potentially have on the distribution of plant species, but few have attempted to constrain projections through plant dispersal limitations. Instead, most studies published so far have been using the simplification of considering dispersal as either unlimited or null. However, depending on a species' dispersal capacity, landscape fragmentation, and the rate of climatic change, these assumptions can lead to serious over- or underestimation of a species' future distribution. To quantify the discrepancies between unlimited, realistic, and no dispersal scenarios, we carried out projections of future distribution over the 21st century for 287 mountain plant species in a study area of the Western Swiss Alps. For each species, simulations were run for four dispersal scenarios (unlimited dispersal, no dispersal, realistic dispersal and realistic dispersal with long-distance dispersal events) and under four climate change scenarios. Although simulations accounting for realistic dispersal limitations did significantly differ from those considering dispersal as unlimited or null in terms of projected future distribution, using the unlimited dispersal simplification nevertheless provided good approximations for species extinctions under more moderate climate change scenarios. Overall, simulations accounting for dispersal limitations produced, for our mountainous study area, results that were significantly closer to unlimited dispersal than to no dispersal. Finally, analyzing the temporal pattern of species extinctions over the entire 21st century showed that, due to the possibility of a large number of species shifting their distribution to higher elevation, important species extinctions for our study area might not occur before the 2080-2100 time periods.

Herbivory in the previous generation primes plants for enhanced insect resistance.

Inducible defenses, which provide enhanced resistance after initial attack, are nearly universal in plants. This defense signaling cascade is mediated by the synthesis, movement, and perception of jasmonic acid and related plant metabolites. To characterize the long-term persistence of plant immunity, we challenged Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum) with caterpillar herbivory, application of methyl jasmonate, or mechanical damage during vegetative growth and assessed plant resistance in subsequent generations. Here, we show that induced resistance was associated with transgenerational priming of jasmonic acid-dependent defense responses in both species, caused caterpillars to grow up to 50% smaller than on control plants, and persisted for two generations in Arabidopsis. Arabidopsis mutants that are deficient in jasmonate perception (coronatine insensitive1) or in the biogenesis of small interfering RNA (dicer-like2 dicer-like3 dicer-like4 and nuclear RNA polymerase d2a nuclear RNA polymerase d2b) do not exhibit inherited resistance. The observation of inherited resistance in both the Brassicaceae and Solanaceae suggests that this trait may be more widely distributed in plants. Epigenetic resistance to herbivory thus represents a phenotypically plastic mechanism for enhanced defense across generations.

Phytochemical investigation of alpine plants : the cottonsedges Eriophorum scheuchzeri Hoppe, E. angustifolium Honck. and E. latifolium Hoppe (CYPERACEAE)

Résumé: Alpine plants living at high altitudes undergo a series of climatic stress factors (chilling, enhanced UV radiation, short growing season, low nutriment supply...) which may influence their secondary compounds composition. Many publications showed in these last years that plants under stress conditions do synthesize a range of specific defence compounds (terpenes, flavonoids, coumarines...). A careful phytochemical investigation of those plants could therefore lead to the discovery of active molecules. Thus, for the biological and chemical screening, about 30 alpine plants have been collected above 2000 metres, in the alpine grass-lands. Eriophorum scheuchzeri Hoppe (Cyperaceae), not yet investigated phytochemically, revealed in its lipophilic and polar extracts the presence of various radical scavengers in a TLC autography with the DPPH (2,2-dipheny1-1- picrylhydrazyl) radical as spray reagent, as well as several antifungal compounds acitve against Cladosporium cucumerinum and Candida albi cans. The first part of this study consisted in the detection, isolation and characterization of the bioactive natural compounds present in the lipophilic extract of Eriophorum scheuchzeri. Among the eight isolated compounds, six were isoflavones. No isoflavones have been reported in the Cyperaceae family yet, nor in related families such as Poaceae or Juncaceae. Besides, isoflavones are generally rare in the plant kingdom and and they occur only in some families, such as Fabaceae, Rosaceae or Myristicaceae. In addition, out of these six isoflavones, three were new isoflavones. The known compounds were parvisoflavone A and B and cajanin which are already known isoflavones in the Fabaceae family. Two of the new isoflavones were particular, as they were C-methylated on the B-ring at the C-3' position. Methylated flavonoids are particularly rare in the plant kingdom. At present, no C-methylated isoflavones with methyl groups on the B-ring have ever been reported. The fourth new compound was a prenylated flavanone. Flavanones are also rare in the Cyperaceae family since they were found only in two genera (Cyperus and Schoenus). Finally, the widespread flavone tricin, characteristic of the Cyperaceae and Poaceae family has also been isolated. The second part of this study consisted in the characterization of the polar components present in the Me0H extract. In order to obtain mass and UV information about the secondary compounds present in the Eriophorum scheuchzeri methanolic extract, a LC-UV/DAD-APCl/MSn analysis has been performed as a first dereplication step. The UV/DAD spectra showed the presence of polyphenol compounds (phenylpropanoids and flavonoids). The LC-APCI/MSn analysis allowed the determination of the molecular weight of these compounds. Moreover, the fragmentation pattern of the [M+H]+ ions indicated presence of mono-, di- and tri-glycosides. LC-UV in combination with UV shift reagents added post-column was used in a second phase for the structural elucidation of the flavonoids. It allowed the positioning of the sugars on the aglycones. Finally, LC-NMR was used for a more detailed structural investigation of the compounds present in the crude MEOH extract. Thus, 10 fiavonoids have been totally or partially characterized by LC-UV-MS and LC-1H-RMN and UV-shift reagents added post column. However, the information obtained on-line was not always sufficient to allow a complete identification of all the compounds. Some of these compounds especially those with more than two sugar units attached to them, have been isolated in order to proceed to their complete characterization. Moreover, the Eriophorum scheuchzeri species was compared to two other species from the same genus. A LC-UV-ESI/MS analysis enabled a survey of the chemical composition of the DCM extracts of two related species E. angustifolium (Honck) and E. latifolium (Hoppe). The chromatograms of the three species showed some similarities in their flavonoid contents, especially by the recurrent presence of three compounds. The MEOH extracts of all three species have been compared by means of LC-UV-APCl/MS analyses. The chromatographic profile of all the three species showed even closer similarities than those found in the DCM extracts. E. angustifolium Honck. and E. latifolium species showed 7 compounds in common. Finally, the pure compounds obtained from the DCM (CH2Cl2) fraction were tested at different concentration, in order to evaluate their chemical and biological activities. All eight compounds showed an anti-scavenger activity against the DPPH radical, and four compounds showed antifungal activities against Cladosporium cucumerinum and Candida albicans. The pure compounds isolated from the MeOH extract were tested only for their biological activities as their antioxidant activity is already well documented in the literature. No compound showed a biological activity against Cladosporium cucumerinum and Candida albicans. Résumé: De nombreux travaux ont démontré ces dernières décennies que les plantes soumises à différents types de stress (basse température, UV, stress hydrique) synthétisent des composés secondaires (fiavonoides, coumarines, terpènes...) de protection et de défense. Les plantes d'altitude par exemple qui sont exposées à des conditions climatiques et environnementales difficiles, ont tendance à synthétiser des substances antioxydantes et antiradicalaires. Une investigation phytochirnique de ces plantes a conduit à la découverte de nouvelles molécules actives. Ainsi plusieurs plantes alpines ont été sélectionnées en fonction de leur habitat en vue de les soumettre aux tests biologiques (antifongiques) et chimiques (antiradicalaires) menés en routine dans notre laboratoire. Dans ce criblage biologique préliminaire, les extraits d'Eriophorum scheuchzeri Hoppe (Cyperaceae) ont réagi positivement aux différents tests. Il a donc été décidé d'entreprendre l'isolement des composés actifs. La première partie de ce travail a consisté à détecter, isoler et caractériser les composés naturels actifs présents dans l'extrait apolaire d' Eriophorum scheuchzeri. Parmi les huit composés isolés, quatre d'entre eux sont nouveaux. Un de ces produits est une flavanone et trois sont de nouvelles isoflavones, particulièrement intéressantes car elles possèdent des groupements C-méthylés au niveau du cycle B. Les flavonoides C-méthylés sont peu répandus dans le règne végétal et les rares exemples connus sont généralement C-méthylés sur le cycle A. Les quatre autres composés isolés n'ont jamais été décrits dans cette famille. Il s'agit d' isoflavones, les parvisoflavones A et B et la cajanine. Enfin, la flavone tricine, flavonoide caractéristique des Cyperaceae et des Poaceae a également été isolée. La deuxième partie de ce travail a consisté à caractériser les constituants polaires présents dans l'extrait methanolique. L'extrait a été analysé par chromatographie analytique couplée à différentes méthodes spectroscopiques (LC-UV-MS et LC-UV-1H RMN). De cette façon, douze flavonoides et un dérivé du phénylpropane, l'acide chlorogénique ont été identifiés. Les flavonoides tri-glycosylés ont dû être isolés afin de déterminer la nature et l'enchaînement des sucres. Finalement, l'espèce Eriophorum scheuchzeri a été comparée à deux autres espèces d' Eriophorum, soit E. angustifolium et E. latifolium. En conclusion, cette étude phytochimique a abouti à l'isolement de plusieurs nouvelles isoflavones aux activités antioxydantes et antifongiques ainsi qu'oestrogéniques.

Remorins form a novel family of coiled coil-forming oligomeric and filamentous proteins associated with apical, vascular and embryonic tissues in plants.

Remorins form a superfamily of plant-specific plasma membrane/lipid-raft-associated proteins of unknown structure and function. Using specific antibodies, we localized tomato remorin 1 to apical tissues, leaf primordia and vascular traces. The deduced remorin protein sequence contains a predicted coiled coil-domain, suggesting its participation in protein-protein interactions. Circular dichroism revealed that recombinant potato remorin contains an alpha-helical region that forms a functional coiled-coil domain. Electron microscopy of purified preparations of four different recombinant remorins, one from potato, two divergent isologs from tomato, and one from Arabidopsis thaliana , demonstrated that the proteins form highly similar filamentous structures. The diameters of the negatively-stained filaments ranged from 4.6-7.4 nm for potato remorin 1, 4.3-6.2 nm for tomato remorin 1, 5.7-7.5 nm for tomato remorin 2, and 5.7-8.0 nm for Arabidopsis Dbp. Highly polymerized remorin 1 was detected in glutaraldehyde-crosslinked tomato plasma membrane preparations and a population of the protein was immunolocalized in tomato root tips to structures associated with discrete regions of the plasma membrane.

Effects of alternative sets of climatic predictors on species distribution models and associated estimates of extinction risk: a test with plants in an arid environment

Aim To evaluate the effects of using distinct alternative sets of climatic predictor variables on the performance, spatial predictions and future projections of species distribution models (SDMs) for rare plants in an arid environment. . Location Atacama and Peruvian Deserts, South America (18º30'S - 31º30'S, 0 - 3 000 m) Methods We modelled the present and future potential distributions of 13 species of Heliotropium sect. Cochranea, a plant group with a centre of diversity in the Atacama Desert. We developed and applied a sequential procedure, starting from climate monthly variables, to derive six alternative sets of climatic predictor variables. We used them to fit models with eight modelling techniques within an ensemble forecasting framework, and derived climate change projections for each of them. We evaluated the effects of using these alternative sets of predictor variables on performance, spatial predictions and projections of SDMs using Generalised Linear Mixed Models (GLMM). Results The use of distinct sets of climatic predictor variables did not have a significant effect on overall metrics of model performance, but had significant effects on present and future spatial predictions. Main conclusion Using different sets of climatic predictors can yield the same model fits but different spatial predictions of current and future species distributions. This represents a new form of uncertainty in model-based estimates of extinction risk that may need to be better acknowledged and quantified in future SDM studies.

Higher plants use LOV to perceive blue light.

Higher plants use several classes of blue light receptors to modulate a wide variety of physiological responses. Among them, both the phototropins and members of the Zeitlupe (ZTL) family use light oxygen voltage (LOV) photosensory domains. In Arabidopsis, these families comprise phot1, phot2 and ZTL, LOV Kelch Protein 2 (LKP2), and Flavin-binding Kelch F-box1 (FKF1). It has now been convincingly shown that blue-light-induced autophosphorylation of the phot1 kinase domain is an essential step in signal transduction. Recent experiments also shed light on the partially distinct photosensory specificities of phot1 and phot2. Phototropin signaling branches rapidly following photoreceptor activation to mediate distinct responses such as chloroplast movements or phototropism. Light activation of the LOV domain in ZTL family members modulates their capacity to interact with GIGANTEA (GI) and their ubiquitin E3 ligase activity. A complex between GI and FKF1 is required to trigger the degradation of a repressor of CO (CONSTANS) expression and thus modulates flowering time. In contrast, light-regulated complex formation between ZTL and GI appears to limit the capacity of ZTL to degrade its targets, which are part of the circadian oscillator.